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Mars dust Explosive vertical storms cause the layers of dust that float kilometres above the Martian surface, new research suggests.

The research by scientists including Dr Aymeric Spiga from the Universite Pierre et Marie Curie, combined orbital observations from the European Space Agency's Mars Express probe, with computer simulations.

"Local dust storms [on Mars] play a key role in the dust cycle, yet their life cycle is poorly known," write the researchers in a paper on the pre-press website ArXiv.org.

Spiga and colleagues focused on an individual, isolated dust storm, which allowed them to see more clearly what was happening than would have been possible in a more complicated environment.

They found sunlight being absorbed by atmospheric dust particles was radiated into the surrounding air, increasing temperatures by up to 20°C, causing the air to rise at speeds of up to 10 metres per second.

This explosive vertical convection, which they've termed "rocket dust storms" or "conio-cumulonimbus", lifts dust particles to altitudes of 30 to 50 kilometres into the Martian troposphere. These dust clouds are then transported horizontally by large-scale winds, forming detached layers of dust.

At night the convection loop stops, but the dust particles float down to the ground only very slowly, resulting in a significant quantity of suspended material remaining in the air the next day when the convection loop starts up again.

The modelling shows the storms reach maximum altitudes in tropical regions throughout the northern spring and summer.

"This can be easily understood since in spring/summer the northern hemisphere receives more incoming sunlight than the southern hemisphere, hence is more prone to strong rocket dust storms conducive to high-altitude detached layers," they write.

The dust layers could be a significant source for atmospheric warming and supply of convective energy, say the researchers.

"Thus we expect rocket dust storms to have a strong impact on the Martian climate which need to be taken into account on global climate models," they say.

Understanding rocket dust storms is also "critical" for the exploration of Mars because the storms may produce strong electric fields, lightning and radio emissions, just like thunderstorms on Earth, they add.

High resolution modelling

Planetary scientist Dr Jonti Horner from says University of New South Wales believes this is the first time modelling has been done on this scale.

"Previously, scientists used global climate modelling which looks at the overall behaviour of atmosphere on a planet-wide scale," says Horner.

"That's good when you don't have a lot of data, but it doesn't pick up localised weather events."

"This new simulation provides finer local resolution for areas of tens of kilometres to a few hundred kilometres across, which is about storm size," he says.

Greater understanding of the Martian atmosphere may also provide a better understanding of Earth's climate, adds Horner.

"The Martian atmosphere is less complicated that Earth's, and so provides us with a test-bed to study individual events without a lot of complications.

"Even though things are a bit different, you'll maybe learn new things about the Martian atmosphere which you can apply to Earth."